1. Field of Invention
This invention relates generally to a serial printer that reciprocally moves a recording head in a direction perpendicular to the direction of movement of a recording paper in order to print thereon. In particular, the present invention relates to the detection of a home or reference position of the recording head.
2. Description of the Related Art
An example of a serial printer is one that is discussed in JP-A-90671/1989. This serial printer comprises a recording head unit, a carriage on which the recording head is mounted; a motor that drives the carriage, a dot pulse generator composed of a disc, containing a slit attached to the motor axis located at the lower part of the motor as well as a photo interrupter, and a home position detector composed of a second photo interrupter that detects the shielding plate attached to the lower part of the carriage. The above-mentioned serial printer when detecting its print position, detects the motor's rotational angle by means of a dot pulse generator and detects the relative print position (dot-to-dot distance) of the recording head during the printing operation. The device detects the home position (or reference start-of-print position), which is the recording head's absolute print position, with of a home position detector. The serial printer disclosed in JP-A-90671/1989 is equipped with position detectors for detecting those positions, and therefore requires two or more detectors. These two or more detectors are additional cost to the printer and require a more complicated circuitry to process these detectors.